Molding sand composition comprising a halogenated aliphatic hydrocarbon as a release agent



United States Patent HALOGENATED ALIPHATIC HYDROCARBON As A RELEASEAGENT Harold K. Salzberg, Bainbridge, N. Y., assigno'r to The BordenCompany, New York, N. Y., a corporation of New Jersey N0 Drawing.Application June 21, 1951, Serial No. 232,871

Claims. (Cl. 260--17.2)

The invention disclosed in this application deals broadly with foundrysand molding methods; deals particularly with foundry sand compositionsespecially suitable for foundry cores, which contain substantialquantities of synthetic resin adhesive to hold the grains of sandtogether in the form of a core, after a baking step; and provides amolding sand composition containing a synthetic resin adhesive, fillers,binders, moisture, and the like, and in addition a high molecular weighthalogenated organic compound which serves to prevent sticking of sandparticles to the core box or to a pattern when a baked mold is used orto other associated equipment.

in the making of metal castings, it has been customary to produce apattern of wood or metal having a size and shape closely similar to themetal article desired, with allowances for draft, metal shrinkage, andthe like; and to ram moist sand around the pattern making provision fora parting surface between cope and drag, together with appropriatesprues, gates, and vents; then to open the mold, remove the pattern, andpour the resulting cavity full of molten metal. However, the making ofholes in such a casting has required the use of cores made of sand inwhich the sand particles are held together with an adhesive, sinceconsiderably more strength is required in a core than is required in thesand mold proper. Early .usage made a core out of a mixture of sand andlinseed oil which was baked for many hours to develop the necessarystrength and cohesion in the core structure. The strength obtained wasbarely adequate, however, and the baking operation was tedious andgenerally unsatisfactory. Current practice tends toward the use ofsynthetic resin adhesives to hold the grains of sand in a core togetherinto a unitary structure, since by the use of setting cat .alysts and asmall amount of heat a strong core is obtained which permits much morerapid operation and much more satisfactory foundry practice. Inaddition, there is a definite trend toward the use of the sameresin-containing sand mix for the making of molds in general, especiallyshell type molds which are highly efficient and satisfactory. However,great difficulty is experienced in obtaining a clean separation of thecore or molding sand from the core box or pattern since all of theadhesives tend strongly .to cause the sand particles to stick to thecore box or pat-tern.

According to the present invention it is now found that, if a smallamount of a halogenated high molecular weight organic compound is addedto the core sand mix or foundry sand mix with the adhesives, theseparation of the core sand or molding sand from the core box or patternis improved so greatly that there is no significant tendency for thesand to stick to the pattern surface; yet adequate green strength isobtained, and excellent baked strength is obtained.

The preferred anti-sticking component is lauryl bromide, but a widerange of other relatively high molecular weight halogenated organiccompounds are also usable. It appears that a carbon atom number betweenabout 5 2 and 25 is desirable; it does not appear that the presence ofone carbon-to-carbon double linkage interferes, nor does it appearsignificant which of the halogens are used, although a brominesubstituted compound is preferable. ,Other objects and'details of theinvention. will be apparent from the following description;

The primary raw materials for the composition of matter of the presentinvention are, first, foundry sand; second, synthetic resin adhesive;third, various addition agents; and, fourth, the halogenated highmolecular Weight anti-sticking compound.

For the foundry sand, any of the usual types and grades of molding sandsare suitable. Molding sands are generally fine in grain size and containsome clay, either naturally present or specially added. Core sands arecoarser and are usually washed free from clay although clayey materialsmay be added in small amounts. Generally the sand is of silica particlesthough there is occa sional use also of zirconium silicate, which is acombination of the oxides of silica and zirconium. Although thebeneficial effect of my invention in the inclusion of the halogenatedorganic compound with the sand applies to all of these grades of sand,it appears to have its most marked elfect in core sands whether the sandis used for cores or for molds in the foundry.

For the synthetic resin adhesive, any of the synthetic resins which arein part water-soluble or are of the hydrophilic type of resins may beused. The preferred resins are the phenol-formaldehyde andurea-formaldehyde types. In preparing these resins the phenol andformaldehyde or urea and formaldehyde are mixed, the condensa tioncatalyst added, the material warmed to an appropriate reactiontemperature,.and the condensation carried to a stage short ofinsolubilization in water. Preferably the condensation is conducted insuch a way as to yield a resin which can be dried to a solid, and groundor powdered, without losing its water solubility. This is desirable, topermit of the making of a dry or nearly dry material suitable forstorage before admixture with the foundry sand.

To the sand-resin mixture there may be added a wide range of auxiliarymaterials. Usually a small amount of water in the range of from 1 partto 6 parts per parts of sand is added to make the sand coheresufiiciently for the necessary handling operations, and give thenecessary green strength. It is also usually convenient to add more orless of a cereal binder, which usually is corn flour, but can be ananalogous material selected from a wide range of such products. Insteadof corn flour, such ma terials as wheat flour or wood flour, or otherinexpensive finely powdered organic material, may be used. In addition,other substances may be added for special purposes, such as silicaflour, iron oxide, bentonite, or the like.

The mixture of sand, resin, and these auxiliary substances makes afoundry sand which follows reasonably closely the prior art and can beused for some purposes. However, very great dilficulty is encountered ingetting smooth, true-shaped cores and molds, because of the very greatstickiness of the cereal binder and resin which causes considerablequantities of the sand to stick to the pattern or core box rather thanto the body of sand, and accordingly it is extremely diflicult to stripthe core from the core box or the pattern from the mold in a cleanfashion so as to leave a perfect core or mold behind.

The essence of the invention, then, is the use or provision of a furtheraddition agent in the form of the above described halogenated highmolecular weight aliphatic compound. The preferred compound, as far asis now known, is lauryl bromide. The addition of lauryl bromide to theabove described components yields a core sand or foundry sand which hasa good green strength, an excellent baked strength, and is completelyfree from any tendency to adhere to the core box or pattern, resultingin practically 100 per cent perfect cores or molds having littletendency for adhesion of the sand to either core box or pattern, andaccordingly no defects in cores or molds from removal of sand particlesby adhesion to core box or pattern occur.

As above pointed out, lauryl bromide is the preferred substance, but anyaliphatic compound having a minimum of about carbon atoms in the linearchain, andat least one halogen substituent, is usable, the maximumfeasible number of carbon atoms being between 25 and 30.

In the practicing of the invention, the sand and resin are convenientlymixed in any desired way, the most satisfactory procedure being drymixing in. a muller. All of the dry components, if desired, may be mixedtogether in the muller and at an appropriate stage in the mixing thenecessary amount of water may be added. The moist prepared mix is thenready for use. The mix is conveniently placed in the core box or aroundthe pattern in any desired way. A core box may be filled by hand ifdesired, or the newer blowing method may be used, depending upon thenumber of cores to be made and many other factors. The core is thenstripped from the core box and the halogenated organic compound servesto give excellent release properties to the sand mix to cause the grainsof sand in the core to adhere together and to release very easily fromthe core box. ,That is, the adhesivity of grain to grain is higher thanthe adhesivity of grains to core box, or pattern. The core shows anadequate green strength, sufiicient to permit of the necessary handlingto put the core into the baking oven. The resin, with a containedsetting catalyst if desired, hardens very quickly in the core oven sothat little more heating is required than enough to bring the entirecore up to setting temperature through the entire body. The resultingcore shows a very excellent baked strength, yet after casting itcollapses sufficiently easily to permit of the neeessary shrinkage ofmetal around the core and does not solidify within the casting to suchan extent as to be difficult to remove,

The details of preferred methods of operation are shown in the followingexamples:

Example I 100 pounds of core sand of New Jersey origin having a grainfineness number of 80 is mixed with vone pound of gelatinized corn flourand 2 pounds of a water syrup of phenol-formaldehyde resin existing inthe so-called A stage of condensation. This mixture is wetted by mixingwith 5 pounds of water. When used at this stage to fill a core box, itis very sticky and will refuse to leave the surfaces of the'core boxclean and free from sand grains. However, if now to this mix thereisadded 0.03 pound or 13.62 grams of lauryl bromide and mixing meansprovided for thorough distribution of this addition among the sandgrains, the nature of the sand is changed to one of non-s ickingcharacteristics and there is no appreciable adheren :e of sand to corebox or pattern surfaces.

Example 2 The sand mix formula of Example 1 is repeated except that tl elauryl bromide is predissolved in kerosene before addition to the sand.An amount of kerosene suificient to provide a concentration of 1 part oflauryl bromide in 5 parts of kerosene by weight will aid in thedispersion of the parting agent on the sand grains, the formula thenbeing 0.03 pound of lauryl bromide in 0.15 pound of kerosene to 100pounds of sand, containing also the synthetic resin binder.

Example 3 For lauryl bromide in kerosene solution as described inExample 2, there may besubstituted halogenated kerosene. Ordinarycommercial kerosene is capable of absorbing enough halogen by merecontact at a warm temperature to produce a compound having the effect 4sought. This is accomplished by passing chlorine into kerosene at atemperature of 14-0l50. F. until the hydrocarbons of the kerosene haveabsorbed at least one per cent of chlorine as determined by analysis.

Example 4 Lauryl chloride is available on the chemical market and hasshown the effect of eliminating sand stickiness to a degree closelyapproaching that of the bromide. Lauryl chloride, like the bromide, isthe alkyl halide of normal structure, C12H25Cl, having the chemicalidentification, l-chlorododecane. While not as effective as the bromide,its cost is lower thus permitting the same high sand release property atequal cost in many core sand mixes. As an example, pounds of core sandis mixed with one pound of corn flour, 2 pounds of phenolformaldehyderesin, and 4 pounds of water. Lauryl chloride in amount of 0.05 pound or22.70 grams is dissolved in 0.15 pound of kerosene and this added to thewet sand mix. After mixing for 1 or 2 minutes, the sand loses its stickynature and can be used in forming molds or cores or on patterns with ahigh degree of release of sand grains.

Example 5 To 100 pounds of core sand, there are added 2 pounds of cornflour and 1 pound of a water solution of liquid urea-formaldehyde resinsolids. Sufficient water is mixed in to give good molding properties tothe sand. While mixing is continued, a solution of 0.02 pound of laurylbromide in 0.15 pound of kerosene is added. A short additional mixingperiod suifices to disperse the parting solution through the sand andrender it non-sticky.

The lauryl or dodecane halides are used in the examples because theseare readily available in the chemical market. However, homologues of thedodecane halide of lower or higher molecular weight are also meant to beincluded in the scope of this invention. It has been observed that theeffectiveness of the alkyl halide improves with increasingmolecularweight in a uniform manner. Some benefit was observed with the halide ofpentane, n-amyl chloride, C5H11Cl, but not with the next lower halide,n-butyl chloride. The halides of lower molecular weight are also toovolatile to be of practical use. The halides of n-dodecane are surpassedin molecular weight by a number of compounds, all believed to beeffective as such or in solution in an inert solvent as molding sandrelease agents.

The halide derivatives of the following hydrocarbons belong to thisseries:

n-Tricosane n-Tetracosane n-Pentacosane n-I-Iexadecane n-Heptadecanen-Octadecane n-Nonadecane Although these examples refer to the use ofthe normal halides because they are being manufactured, it is notintended that the isomers of these compounds, that is, the derivativesin which the halogen is located in other than the 1-position, or thecorresponding isomeric compounds with respect to the chain structure ofthe molecule, shall be disregarded.

The names used here, such as lauryl bromide, are sometimes wrongly usedto designate the acid halides, RCOX, where R is the alkyl group and Xthe halogen. The acid bromide corresponding to lauryl bromide isproperly referred to as lauroyl bromide. This invention is not intendedto cover the use of the acid halides for this pumo c- Thus, thecomposition of matter of the invention produces a core, or mold, havinggood green strength, excellent baked strength, excellent releaseproperties of sand from pattern or core box, quick baking, and readycollapsibility after pouring of the molten metal. The process involvesthe mixing together of sand, resin, fillers, and a halogenated organiccompound having from 5 to 30 carbon atoms in the linear chain, themoistening step, and forming in a core box or against a pattern,followed by baking of the resulting form to yield an excellent core ormold around or within which molten metal can be poured to yield thedesired shape, while the core collapses readily under the contractionalforces of the cooling metal.

While there are above disclosed but a limited number of embodiments ofthe composition and process of the invention, it is possible to providestill other embodiments without departing from the inventive conceptherein disclosed; and it is therefore desired that only such limitationsbe imposed on the appended claims as are stated therein or required bythe prior art.

The invention claimed is:

1. A sand molding composition for preparing molds for casting moltenmetals comprising a mixture of foundry sand constituting the major partof the mixture, a heatcurable binder composition containing ahydrophylic resin selected from the group consisting of condensationproducts of formaldehyde with phenol and formaldehyde with urea, inproportion adequate to bond the same, and, as a release agent, akerosene-soluble C5--C30 substituted aliphatic hydrocarbon containing assubstituent one halogen atom to the molecule, the halogen being selectedfrom the group consisting of chlorine and bromine and the proportion ofthe release agent being less than the proportion of the binder.

2. The composition of claim 1 including a ground cereal binder inproportion less than that of the sand.

3. The composition of claim 1 in which the release agent is amonohalododecane in which the halogen pres cut is selected from thegroup consisting of chlorine and bromine.

4. A sand molding composition for preparing molds for casting moltenmetals comprising a mixture of foundry sand constituting the major partof the mixture, a heatcurable binder composition containing ahydrophylic resin selected from the group consisting of condensationproducts of formaldehyde with phenol and formaldehyde with urea, inproportion adequate to bond the same, and, as a release agent, kerosenechlorinated to a content of approximately 1% of chlorine.

5. A sand molding composition for preparing molds for casting moltenmetals comprising a mixture of foundry sand constituting the major partof the mixture, a heat-curable binder composition containing ahydrophylic resin selected from the group consisting of condensationproducts of formaldehyde with phenol and formaldehyde with urea, inproportion adequate to bond the same, and, as a release agent,mono-l-bromododecane.

References Cited in the file of this patent UNITED STATES PATENTS1,837,877 McDowall Dec. 22, 1931 2,045,913 Hoy et al June 30, 19362,127,535 Saeger Aug. 23, 1938 2,306,222 Patnode Dec. 22, 1942 2,358,002Dearing et a1. Sept. 12, 1944 2,372,236 Wainer Mar. 27, 1945 2,388,299Thielemann Nov. 6, 1945 2,425,978 Anderson Aug. 19, 1947 2,466,667Thomas Apr. 12, 1949 2,665,261 Baker Ian. 5, 1954 OTHER REFERENCESOrganic Chemistry by Karrer, published 1938 by Elsevier of Amsterdam andNew York, page relied upon.

Chemical and Metallurgical Engineering, September 1944, page 33.

Phenolic Resin Core Binders, published by Monsanto Chemical Co., pages 8and 9. Reprint of address delivered May 8-12, 1950, in Cleveland.

Bakelite Phenolic Resins, published by Union Carbide and Carbon Corp.Copyright 1950, 13 pages, 6 and 13 relied on.

1. A SAND MOLDING COMPOSITION FOR PREPARING MOLDS FOR CASTING MOLTENMETALS COMPRISING A MIXTURE OF FOUNDARY SAND CONSTITUTING THE MAJOR PARTOF THE MIXTURE, A HEATCURABLE BINDER COMPOSITION CONTAINING AHYDROPHYLIC RESIN SELECTED FROM THE GROUP CONSISTING OF CONDENSATIONPRODUCTS OF FORMALDEHYDE WITH PHENOL AND FORMALDEHYDE WITH UREA, INPROPORTION ADEQUATE TO BOND THE SAME, AND, AS A RELEASE AGENT, AKEROSENE-SOLUBLE C5-C30 SUBSTITUTED ALIPHATIC HYDROCARBON CONTAINING ASSUBSTITUENT ONE HALOGEN ATOM TO THE MOLECULE, THE HALOGEN BEING SELECTEDFROM THE GROUP CONSISTING OF CHLORINE AND BROMINE AND THE PROPORTION OFTHE RELEASE AGENT BEING LESS THAN THE PROPORTION OF THE BINDER.